Jim,
First, what he said (Stealth 6, post 5, above.) I love your projects! And, thank you so much for your guidance in the past.
Matt
You're welcome! I'm glad you pointed out S6's post. That one came in while I was responding to the one below it, and I didn't see it.
I'm reluctant to lift the rail in a way that puts torque on the rail or on the point where the rail attaches to the pad. Some torque is OK, but there is no way that I would lift the far end of the rail only.
My version of the geometry is in the attached pic. Pad Slave #1 is pretty tall. Let's assume that with some help (2 Pad Slaves on the other side of the CG), he could hold up the rail at a point 1' beyond the CG to a height of 8'. This puts the rail at an angle of 33 degrees to the ground. For reference, the distance between the fulcrum and the CG is 10' (1' of pad support and 9' of rail) and the weight at the CG is 210#.
Now, let's assume Pad Slave #2 grabs the clamshell rod at a point 5' from the fulcrum. He hangs off this rod and is able to apply a force perpendicular to the rod of 60#. That relieves 5/10x60=30# of the 210# weight. Let's also assume that Pad Slave #3 pushes at a point midway between the CG and the fulcrum. If he pushes perpendicular to the rail at 60#, that relieves another 30# of the 210# weight. Agree?
So, when Pad Slave #1 lets go, we have to make up 150# of force to hold the rail where it is. One option is to have Pad Slaves 4 and 5 grab the T bar and lift at 75# each (or angle the T bar more perpendicular to the rail and lift at 63# each). As the rail goes up, the weight they have to lift goes down as the mechanical advantage for Pad Slaves 2 and 3 improves. The initial weight, though, just seems like a little too much to me? Yes, the T bar could be placed outside of the CG, but that applies a torque to the rail and the rail attachment point.
Alternatively, one could use a rope. The "rope" in the pic is a 50' rope held 4' off the ground. For the angle shown, I calculate that the rope would have to be pulled with a force of 260# to hold the rail static (i.e., to hold the 150# remaining weight). Can someone check this calc? It assumes 126# upward force needed perpendicular to the rail, with 260# of pull resulting in 126# perpendicular to the rail and 227# down the rail.
Let's assume that a Pad Slave could pull tug-of-war style with a force of 30# (it's sandy out there). That would take 9 Pad Slaves (plus the Slave on the clamshell rod and the Slave pushing between the fulcrum and the CG). I don't have that many Pad Slaves! That would take a winch. Or perhaps a couple of Pad Slaves pulling on the rope could reduce the weight at the T bar a bit? Or perhaps I can just tie a rope to my truck and pull it up that way?
I believe that the rope at the CG would apply a force down the rail (about 227#) but would
not apply a radial torque to the rail or at the point of attachment. Agree? This is important!
As a relatively minor point, pulling at the clamshell and pushing between the CG and the fulcrum will apply a counterclockwise torque where the rail attaches to the pad. Thus, it might be better to attach the rope a little higher on the rail, which would apply a "clockwise" torque at the point of attachment. Agree?
If one used a rope and winch only (i.e., no Pad Slaves at all), the required pull on the rope would be 364# and the force down the rail would be 318#. This might be OK as long as there is no torque on the rail. The resultant horizontal force on the pad, applied at the fulcrum, would be 305# (I think this is right?). Most likely, the pad would want to slide. I think it would be possible to attach guide wires to the fulcrum area and stake these down such that the pad won't slide. Make sense?
After considering the above, I'm thinking the best way to do this would be to have 3 Pad Slaves lift the rocket to the position in the pic, support the rail in that position with a 2x4, and then raise the rail with a winch attached to a vehicle, with a rope/wire attached to the CG, with no Pad Slaves near the rocket. This really depends on the lift not torquing the rail, but if the rail failed, the rail/rocket would just fall with no one getting hurt. PLEASE give me some feedback on the calculations and this plan.
Jim